Please refer FIG. 1(a), which illustrates a conventional master/slave current distribution circuit for a parallel power supply according to the prior art. The conventional master/slave current distribution circuit 1 includes a voltage amplifier 11, an impedance 12, a power converting unit 13, a detecting unit 14, an equivalent diode 15, an adjustable amplifier 16 and an adder 17. The distributions of the output voltages and the output currents of the first power supply PS1 and the second power supply PS2, which are electrically connected in parallel, are able to be stabilized through the operation of the master/slave current distribution circuit 1, which is electrically connected to the first power supply PS1 and the second power supply PS2.
In order to prevent the output unstability resulted from the parallel error between the first power supply PS1 and the second power supply PS2, a gap voltage is provided in the master/slave current distribution circuit 1. For examples, it is feasible to use the equivalent diode 15 as a discrete component for generating a non-linear gap voltage in the linear operating range, i.e. 0˜0.4 V. Such a non-linear gap voltage, however, will result in a unstable outputs of the first power supply PS1 and the second power supply PS2 while the value of the gap voltage is too large.
For overcoming the forgoing drawback, a conventional technical scheme, i.e. the droop method, has been developed in the prior art. The droop method relates to obtaining an operation slope S through the equation “S=ΔV/V0 max.” while the master/slave current distribution circuit 1 is operated under a load from zero to the maximum, wherein ΔV is an applied voltage range of the master/slave current distribution circuit 1 and V0 max. is the maximum value of the output voltage.
However, there is still a drawback in the conventional droop method. When the operation slope S is small, i.e. ΔV is smaller or V0 max. is larger, the error of the parallel power supply will be too large to make the first power supply PS1 and the second power supply PS2 electrically connect in parallel successfully under a light-load. Please refer to FIG. 1(b), which illustrates the relationship between the single output current and the total output current, and the large error between the first and the second power supplies is also shown therein. Moreover, the voltage differences between the first power supply PS1 and the second power supply PS2 must be small enough for being well electrically connected with each other in parallel. Furthermore, the drift of the temperature or the error resulting from the electronic components will also result in an unsuccessful parallel connection between the first power supply PS1 and the second power supply PS2.
In order to overcome the drawbacks in the prior art, an improved master/slave current distribution circuit is provided in the present invention.